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What was it like the last time CO2 levels were this high?

Posted on 16 April 2011 by John Cook

A vivid picture of our climate's future can be found in our past. Currently, atmospheric carbon dioxide (CO2) levels have reached 390 parts per million (ppm). The last time CO2 was that high was around 3 million years ago, during the Pliocene. Back then, CO2 levels remained at around 365 to 410 ppm for thousands of years. Consequently, the Pliocene gives us vital clues of the long-term effects of raised CO2 levels. New research has just been published that examines this period and confirms previous findings that  the Pliocene  was dramatically warmer than current temperatures.

The research, published in Csank et al 2011, uses two independent methods to measure Arctic temperature during the Pliocene, on Ellesmere Island. They find that Arctic temperatures were 11 to 16°C warmer (Csank 2011). This is consistent with other independent estimates of Arctic temperature at the time. Global temperatures over this period is estimated to be 3 to 4°C warmer than pre-industrial temperatures.  Sea levels were around 25 metres higher than current sea level (Dwyer 2008).

This tells us our climate is sensitive to changes in CO2. If we were to stabilise CO2 levels at around 400 ppm, we'd expect over the long-term a further warming of 2 to 3°C, which is significantly greater than the warming predicted by climate models. This is because climate models only include short-term feedbacks, such as increased water vapor and melting of sea ice. They are yet to take into account the long-term feedbacks from the melting of ice sheets and vegetation changes.

This also tells us that ice sheets are sensitive to sustained warmer temperatures. The Greenland and Antarctic ice sheets lost significant amounts of ice during these warmer temperatures. This sensitivity is apparent in current observations, with both Greenland and Antarctica losing ice at an accelerating rate.

The ice loss is particularly dramatic in Greenland. Two decades ago, the Greenland ice sheet was in approximate balance - ice loss at the edges as glaciers calved into the ocean was balanced by ice gain in the interior from increased snowfall. One decade ago, the ice loss at the edges had increased and Greenland was losing around 100 billion tonnes of ice every year. Currently, this ice loss has increased to around 300 billion tonnes of ice per year.

Earth's past history is sending us a strong message - current CO2 levels are not safe. This is echoed by movements like 350.org who tell us we need to stabilise CO2 levels at 350 parts per million. That means dramatically reducing carbon emissions and looking for ways to remove CO2 from the atmosphere or we may eventually face the potentially catastrophic conditions of the Pliocene once more.

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Comments 1 to 50 out of 67:

  1. This appears to be in close agreement with Hansen's 2008, Target Atmospheric CO2: Where Should Humanity Aim?. In that paper, there is much discussion about the differences between fast and slow feedback processes.
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  2. Actually CO2 levels have not been this high since about 15-20 million years ago, when the planet saw falling CO2 levels from the PETM. C02 levels even at this level (393ppm) sustained will mean severe problems for us- past 400ppm this increases exponentially- at 450ppm, 2-3 degrees C is a certainty- with all the complications associated with it- and they will be very harsh.
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  3. There is also good discussion about climate sensitivity and how it is not really a constant, in the above article. Not always, but I have seen it treated that way. An easy way to think about non-constant sensitivity is to think of some feedback in particular, for instance, ice sheets. On an ice-free planet, a little more warmth produces no ice->ocean feedback, and on a ice-ball earth, a little less warmth does not change the albedo. In between, I suspect it has a lot to do with the layout of the continents and how that interacts with Milankovitch cycles.
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  4. but I really don't understand : if the variation is not due to an external cause and not the injection of CO2, what is really measured is the sensitivity of CO2 with respect to temperature , not the sensitivity of temperature to CO2 - in other term, it is the other factor of a retroaction loop B=dCO2/dT and not A = dT/dCO2 (actually the dT/dCO2 is B^-1)

    what is true is that the product A.B = f , the retroaction factor, giving eventually a 1/(1-f) amplification factor. But f must be <1 to avoid a catastrophic runaway, meaning B^-1 > A , so the dT/dCO2 measured is an upper bound of the sensitivity - NOT the sensitivity.

    Of course a large amplification factor means f close to 1, so B^-1 is close to A , giving an approximate equal value. However this assumes that f is really close to 1 ...
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  5. 4, Gilles,
    ...but I really don't understand

    The first accurate thing I've seen you post all week.

    Seriously, though, in this case you are confusing yourself, and making things far more complicated than they need to be.

    Why do you say "if the variation is not due to an external cause and not the injection of CO2?"

    That statement makes no sense to me, because I don't see where it came from.

    You go on to say:
    ...what is really measured is the sensitivity of CO2 with respect to...

    What is measured is not CO2 with respect to temperature or sensitivity of temperature to CO2. What is measured is sensitivity of temperature to temperature. That is, any forcing that drives the temperature up (or down) by X will actually drive it up (or down), after all feedbacks have come into play, by a total of 3X to 4X.

    It doesn't matter if the initial forcing is from CO2 or something else, or if part of the positive feedback is from CO2.

    The takeaway from this is that if we drive CO2 to a point where we expect it to raise temperatures by 1˚C, climate sensitivity will further drive temperatures farther up by a total of 3˚C to 4˚C.
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  6. The Wikipedia article on Pliocene Climate, http://en.wikipedia.org/wiki/Pliocene_climate, does not make it sound like there were any "potentially catastrophic conditions of the Pliocene".

    So this could use more explaining in the article -- unless SkS is successful in adding a description of those conditions to Wikipedia.
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  7. "The Wikipedia article on Pliocene Climate, http://en.wikipedia.org/wiki/Pliocene_climate, does not make it sound like there were any "potentially catastrophic conditions of the Pliocene"."

    What's catastrophic is a magnitude/location/effect on people issue. Humanity has experienced the end of the last ice age, with a rise of sea level of over 100 meters, a quarter of which is projected for this partial pressure of CO2 in the long run. It's just there are not anymore many places to run to, if/when a local catastrophe aggravated by rising seas hits some coastal city.

    Pliocene climate itself doesn't sound too bad, though likely there were tropical areas too hot for humans (who weren't present yet). Humidity was likely high and grassfields/savannas fewer than currently (might this have had something to do with molds and other plant pathogens, can't say). Forests possibly grew ever higher and partly induced their own diminishement at the Pliocene-Pleistocene boundary set by the first larger glaciation at Greenland/Arctic, Panama strait closure being the main reason, cutting the Atlantic off the tropical ocean currents and beginning the current mode of thermohaline circulation with the amount of Arctic ice, Bering Strait closure/opening, and Milankovich cycles, as the main moderators of the NH glaciations/deglaciations. (The overall warming signal should be less noisy in the SH than in the NH.) Now this is starting to drift off topic so I'll stop.
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    Moderator Response: [DB] Fixed text.
  8. How many times do we have to say its not the future temperature that is the main worry but speed of getting there. It all about rate. Adaption is easy if you have a million years to do it - hell if its only 100 years. The Pliocene is a window on what world could look like. Some parts of the view could happen quickly, others slowly (there is limit to how fast you can melt ice).
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  9. "...we may eventually face the potentially catastrophic conditions of the Pliocene once more."

    @7 jyyh:

    "What's catastrophic is a magnitude/location/effect on people issue."

    Jyyh; I agree with your point. However, the last sentence in the post states "once more". It doesn't sound good since back then there was no civilization that would suffer a catastrophe and the situation was not 'catastrophic' to our ancestral Australopithecines back then.

    The people issue in my opinion is related to the fragility of civilization. Hence, that sentence would better read:

    "...we may eventually face conditions that our fragile civilization cannot adapt to, in the short time given."

    This brings us to a secondary but important issue that was brought out by Scaddenp @8. When comparing globally warm situations in the past with the present, mention should be made of the fact that AGW is progressing faster than natural warming events. Then one should emphasize how civilization cannot adapt to such rapid changes.
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  10. Sphaerica : so what was the cause of initial CO2 variation ?
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  11. scaddenp #8
    Two questions :
    a) what is the warming rate which mankind is supposed to be unable to adapt ?
    b) why is it supposed to be unable to adapt to a change of temperature and able to adapt to giving up 80 % of its energy sources in some decades ? which can of rate does it give compared to historical ones ?
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  12. Humanity will adapt - what actual studies we have just show that more expensive in money and lives than curbing emissions. Feel free to point me to studies that are more creditable.

    Many other species wont.

    b/ Sorry I dont buy the "have you stopped beating your wife yet" debating trick. This thread is about CO2 in pliocene. Your question has been answered exhaustively in other places on this site and in other blogs.
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  13. "b) why is it supposed to be unable to adapt to a change of temperature and able to adapt to giving up 80 % of its energy sources in some decades ?"

    Wow, you really are a 1-track album, aren't you Gilles? In little more than 50 years, humanity went from the Wright Brothers to Supersonic Jet planes, long-distance air travel & even putting objects & humans into space. Yet you constantly question our ability to replace outdated fossil fuels with clean & reliable renewable energy in a similar space of time.
    Still, as you clearly get all your info from sites devoted to the fossil fuel industry, I can't say I'm entirely surprised by that.
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  14. "Sphaerica : so what was the cause of initial CO2 variation ?"

    You are aware, Gilles, that the Pliocene marks the end of the Tertiary Era, when the Earth's atmosphere was still relatively rich in CO2-& other Greenhouse gases-from *millions* of years of volcanic activity between the Permian & Cretaceous eras? It wasn't until the Quaternary Era (the Pleistocene & younger) that CO2 levels reached those that we've known for the better part of 1 million years (well, until the last 50 years or so).
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  15. The early to mid Pliocene was markedly warmer then today. The American heartland was mostly desert. Human ancestors where in east Africa (Australopithecus). It has been suggested that, during the Pliocene (ca 5–1.8 Ma), an El Niño state existed as a permanent rather than an intermittent feature;

    The global average temperature in the mid-Pliocene (3.3 mya - 3 mya) was 2-3°C higher than today, global sea level 25 m higher-Northern hemisphere ice sheet mostly non existent in the arctic- or short lasting in duration mid winter.
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  16. Thanks for that perspective, newcrusader.

    It's one thing to talk in abstract figures, but another to point out some of the local climatic details. It brings it home a little more clearly.
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  17. "It wasn't until the Quaternary Era (the Pleistocene & younger) that CO2 levels reached those that we've known for the better part of 1 million years (well, until the last 50 years or so).
    "
    But yet CO2 varied in a non monotonous way - so again what makes it vary ? Just saying "the temperature was X and CO2 was Y " doesn't prove that CO2 is the main driver.

    Now actually as I said it can be considered as the main driver * if the amplification factor 1/(1-f) is large * (what Sphaerica incorrectly calls the "temperature to temperature feedback") (which means actually f = A.B smaller but close to one). In this case, the main cause of temperature variation is indeed the amplified response, and not the initial perturbation, that becomes actually irrelevant. But this is exactly the same condition as B^-1 ~ A

    The important point however is that this is a self-consistent, but circular hypothesis. I mean that IF you consider that the amplification factor is large, you will be satisfied because is the sensitivity to CO2 to temperature (B) is low, than its inverse B^-1 is large and you will be inclined to interpret it as a "high " A climate sensitivity (in more concrete words : if CO2 varies little with temperature and that you *postulate* that the temperature varies only because of CO2, you must conclude that the sensitivity to CO2 is high).

    But it doesn't exclude other hypothesis , namely, that the f factor is low, that B^-1 is NOT equal to A, and that temperature varied because of other things that CO2. You just track the low sensitivity of CO2 to temperature, and that's all. This would equally well work - in other words, the system is under-constrained if you only look at one type of variation.
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    Moderator Response: [Dikran Marsupial] If you want to know what causes the variations in CO2 on different timescale (different mechanisms are involved), then stop trolling, step away from your computer and go and do some reading and find out. There is a very good book on the carbon cycle by David Archer, which would be a good place to start.

    I am amused that after your protestation that you understand falsificationism, yet again you are saying X doesn't prove Y. No observation proves any hypothesis; nobody is claiming that X proves Y, so you are trolling with a straw man, yet again.

  18. Thank you Bern for the nice words. The perspectives I gave above are predicated on C02 levels from about 380-400ppm, which are fairly good estimates of the mid Pliocene, from current data.
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  19. How does this fit with Tripati's work suggesting we are currently higher than the Pliocene, with the last time CO2 levels being this high being 15 million years ago?

    http://newsroom.ucla.edu/portal/ucla/last-time-carbon-dioxide-levels-111074.aspx
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  20. 17, Gilles,

    For some reason you are focused on variations which are never mentioned, and the cause of the CO2 levels in the Pliocene.

    There were no notable variations, and the cause of the CO2 levels is not the focus of the post. Please stay on topic.

    From the text of the post:

    CO2 levels remained at around 365 to 410 ppm for thousands of years. Consequently, the Pliocene gives us vital clues of the long-term effects of raised CO2 levels.


    Stick to that, please.
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  21. Spike25

    I have read Tripati's research at UCLA- I agree with her that we have not C02 levels since around 20 million years ago (see my #2 above)
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  22. MattJ

    Actually, the problem is the pace of the change.
    If the Earth warms 3 degrees in millions of years, new ecosystems will evolve, species will adapt, new species will appear.

    Do it in one or two centuries, and the change will be too fast for everyone. Including humans that built their whole civilization in the stable Holocene climate.
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  23. 3 degrees rise by 2050 or 60 now seems possible- 4 degrees by 2099 probable. A 4 degree rise in just over 100 years means that most species will not adapt, including us- as Alexandre said.
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  24. 20 Sphaerica and 17 DM :

    What I'm saying is that there is a flaw in "consequently" - because it assumes that what is to be demonstrated, that we see "the effecs of raised CO2 levels" : for it is nowhere demonstrated that we don't see rather the effects of temperature on the CO2 level.

    DM : again I'm contesting the use of a "undismissed" theory which allows other "undismissed" theories. While you're right in your assertion about falsificationnism, you don't seem to understand its use : it's that you can gain confidence in a theory only after disproving all reasonable other explanations. What I'm saying is that nothing in what is written disproves alternative explanation - that you mainly track natural sensitivity of CO2 to external causes of temperature changes (whatever these causes are), and this is not the same that what you seem to look for - the sensitivity of temperature to CO2.
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    Moderator Response: [Dikran Marsupial] No Gilles, as has already been pointed out to you, where there are multiple competing hypotheses, none of which have been excluded by the observations/experiment, then you apportion "belief" to each hypothesis according to the strength of the evidence. It is not correct that all unfalsified hypotheses are equally plausible. The "consequently" is just saying the evidence points towards a hypothesis being true, that is all. Popperians call this "corroboration", and they are happy with the idea that hypothesis become stronger the more corroborated they are.

    However the hypothesis that the post-industrial increase is due to the effects of rises in temperature, rather than the other way round, is falsified by the observations. The matter has been discussed numerous times here on SkS, so find an appropriate article where it has been discussed, read the arguments presented there, and I will be happy to discuss it with you (not as moderator) further on that thread - but not here.

  25. Gilles#24: "for it is nowhere demonstrated that we don't see rather the effects of temperature on the CO2 level."

    Yet another unsubtantiated bit of hand-waving; another attempt to drag discussion off-topic. If you are claiming that rising temperature increases CO2, find the appropriate thread -- and this time, read it before offering more opinions.
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  26. " It is not correct that all unfalsified hypotheses are equally plausible."
    Maybe , but you have to prove they're not equally plausible - and there is evidence that at some times in the last million of year , a decrease of CO2 lagged a decrease of temperature.

    "If you are claiming that rising temperature increases CO2,"
    well please let me know what else could increase CO2 ! and I'm precisely arguing this is relevant to this topics, because you have to disentangle which is the cause of which.
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    Moderator Response: [Dikran Marsupial] As I said, if you want to discuss whether temperature is the cause of the post-industrial rise in CO2, or vice versa, please do it elsewhere, it is off-topic here. If you raise this topic again on this thread, the post will be deleted, you have been warned. This is not censorship, you are welcome to discuss it on a more appropriate thread.

    This thread would be particularly appropriate.

  27. " As I said, if you want to discuss whether temperature is the cause of the post-industrial rise in CO2,"
    But that's not what I'm discussing - I was discussing variations of CO2 in the last millions years: if it's not temperature, what else ?
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    Moderator Response: [Dikran Marsupial] On a scale of thousands of years plus, CO2 levels are largely governed by exchanges with the oceans (which depends on a number of factors, including temperature). On longer timescales by the "chemical weathering thermostat". CO2 is also produced by volcanic activity. On shorter timescales, they also vary with internal variability, e.g. ENSO etc. The book by David Archer that I mentioned earlier explains all this in some detail.
  28. Do you mean that there can be spontaneous variability in the CO2/temperature/oceans system even without a injection of CO2 ? interesting -I thought it was impossible.

    Nevertheless , unless you justify that the warm period in Pliocen was triggered by massive injection of CO2 from volcanic activity, it corresponds to what I'm saying, CO2 is a response, not a driver. The fact that it enters a feedback loop doesn't change the situation, because amplification acts on both - CO2 and temperature - and so conserve the initial ratio.

    { - snip - long-winded, off-topic overly mathematical derivation of feedback removed - }


    In other words, if the amplification factor is *not* large, the CO2 responds only linearly to the "other causes" and its relative part in the global temperature change is minor.

    I know perfectly that you think it is not the case - but that the amplification factor is large and that CO2 plays a major role - but I haven't seen yet a decisive evidence for that, and I like more explanations to justifiy it.
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    Moderator Response: [muoncounter] Variability of atmospheric CO2 in geologic history is the subject of numerous other threads. Before you continue theorizing, please familiarize yourself with some basic tenets of geologic processes.

    Your other points(?) are addressed in several sensitivity threads. Rather than merely calling for others to bring you evidence, you might consider engaging in some actual research of your own.

  29. "Earth's past history is sending us a strong message"

    The OP is claiming this as a fact while it is an interpretation of earth's history. What reason do the OP think is talking against this interpretation and why should they be ignored?
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    Moderator Response: [DB] Could you rephrase your question a bit more clearly? As written, it is a bit difficult to parse.
  30. Spike25,
    I would say that the Csank article above is in the same line as earlier Tripati work, but that is not surprising since Tripati is one of the 'et al' authors.

    Gilles,
    I think you should step back and model this as a kind of multi-body problem; whenever one thing changes, all things change. The physics which are used to determine that CO2 is a GHG are well understood. More CO2 causes a warming, but it is not the only thing affecting the climate and humans are not the only thing affecting CO2. How much carbon is sequestered is partly a function of climate conditions, but also continental plate subduction plays a role, etc. However, our production of CO2 through industrial (including agriculture) processes is they only thing that has changed significantly in the last 100 years or so.

    We know it is getting warmer, and that it will continue to do so; the discussion is about how much and how fast. Feedbacks are everything, and the indication from the above article and others is that the feedbacks will largely amplify the base CO2 effect. Climate models predict this, but we know that climate models are incomplete. That is the nature of models. However, the article above is about the system itself, which by definition has all feedbacks in place and fully accounted for. In the Pliocene, the position of the continents, the output from the sun, and the orbital mechanics are largely the same as they are now; so, we should expect a similar thermodynamic equilibrium from a similar atmospheric composition.

    I also highly recommend Archer's book "Global Warming: Understanding the Forecast". It covers the basics from the interaction of IR with CO2 molecules on up, but it is not too technical for someone with the skills you have demonstrated. I suspect you are just missing a piece or two of the puzzle and that is skewing your understanding.
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  31. @11 Gilles:

    "Two questions :
    a) what is the warming rate which mankind is supposed to be unable to adapt ?"


    Gilles, oh Gilles. Please keep in mind that there is a difference between humanity per se and civilization. James Lovelock, author of the Gaia Hypothesis and believer in CAGW, says that as little as 100 million human beings would survive.

    It's even possible to say that (micro) civilizations could exist under the condition he foresees. You only need a few tens of thousands to fulfill the definition of civilization.

    So would you please rephrase your question based on the potential numbers of a reduced population? Even that would be a silly question to ask; a worthy one but silly nonetheless, due to the enormous difficulty (impossibility?) of calculating the techno-social effects on humanity based on X rate of warming.

    Human beings are much more difficult to predict than warming rates. That's due to psychology, stupidity and (panic based) ingenuity.

    I hope you're young. You'll get at least part of the answer to your question(s) without any math or even science. Live long and...
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  32. Giles@28 It is not as simple as whether CO2 is a control or a response. It is one part of the wider climate system, and it both influences responds to the other components, generally CO2 tends to respond rather than to initiate; but there have been occasions when CO2 has driven climate change. For instance the emergence from the Snowball Earth is hard to explain without the accumulated CO2 emissions from volcanic activity. The position of the continents can also affect climate by changing rates of chemical weathering (hence changing CO2 levels), which is an example of CO2 initiating a change in climate. I remember reading an interesting paper in Nature about a period of cooling caused by increased weathering as a result of the uplift of the Appalacians (sorry can't find reference at the moment).

    The Carbon cycle is the key mechanism that has stabilised the Earths climate for millions of years (see this paper). Personally I think calling it a "control" is only really meaningful in a post-industrial setting, because anthropogenic emissions now control the level of CO2 in the atmosphere and hence have a major influence on the climate. Prior to that, the natural carbon cycle acts much more like a thermostat (see Archer book).

    As to what caused the Pliocene warm period, I don't know, it seems to me unlikely we will even "know" what caused particular paleoclimate events. However, I don't really see the relevance to the discussion. CO2 is a greenhouse gas; its effect on climate is the same, regardless of what caused it to be in the atmosphere.

    For modern climate, it doesn't matter if the natural response of CO2 to "other causes" is linear or not (I assume you mean natural causes), as we know that the post-industrial rise in CO2 is not a natural phenomenon. This is one of the few things in climatology that we can be sure of. We have circumvented the "natural response" with anthropogenic emissions.
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  33. ChrisG : "In the Pliocene, the position of the continents, the output from the sun, and the orbital mechanics are largely the same as they are now; so, we should expect a similar thermodynamic equilibrium from a similar atmospheric composition."

    Really? why has it cooled meanwhile, then ?

    Villabolo : "Gilles, oh Gilles. Please keep in mind that there is a difference between humanity per se and civilization. James Lovelock, author of the Gaia Hypothesis and believer in CAGW, says that as little as 100 million human beings would survive."

    would survive what ?

    As far as I know, the huge increase of population is correlated with an increase of FF consumption and an increase of temperature - so if any, the "negative" influence of increasing temperature has been largely offset by the positive effect of energy availability - or the huge modern demographic growth would be totally incomprehensible.

    Now please give me a simple argument to tell me when the negative effect of an increase of temperature would be much larger that the positive effect of increasing energy consumption -and conversely the positive effect of avoiding the increase of temperature would be much larger that the negative effect of suppressing 80 % of the energy consumption- since the whole history demonstrates exactly the opposite ?

    DM : I am completely ready to admit that CO2 contributes to warm the atmosphere , on very simple arguments of radiative transfer. My only questions are quantitative.
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    Moderator Response: [Dikran Marsupial] If your questions about CO2 as a greenhouse gas are quantitative, then there are a variety of threads here that examine climate sensitivity. There are many knowledgeable contributors here who I am sure would be happy to discuss quantitative issues with you there. If you are not happy with GCMs, you might want to look at earlier work by Gilbert Plass performed back in the 1950s and getting a result in the same ball park as today's GCMs (see RC article for caveats).
  34. Gilles wrote : "Really? why has it cooled meanwhile, then ?"


    What has cooled, and since when ?
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  35. Gilles#33: "the huge increase of population is correlated with an increase of FF consumption and an increase of temperature"

    Ah, the good old correlation equals causation game. We can use that now?

    "please give me a simple argument to tell me when the negative effect of an increase of temperature would be much larger that the positive effect of increasing energy consumption"

    Apparently you missed the more than 30000 deaths during the European heat wave of 2003? Odd that a society so rich in the positive effects of energy consumption would suffer so much hardship during a mere localized heat wave.

    Firefighters know this to be true:

    “It is easier to stay warm than it is to stay cool in all this gear,” he said. “Once you get overheated, it is really hard to get cooled off. You have to be out in the cold like this a long time before it will affect you systemically, whereas in the heat like that, in 15 or 20 minutes, guys start dropping if you don’t rehab them.”
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    Moderator Response: Gilles, a more relevant thread for your claims is "It's Not Bad."
  36. Here as an interesting article along the same lines where Csank was a co-author,
    Significantly warmer Arctic surface temperatures during the Pliocene indicated by multiple independent proxies
    (No pay wall)


    Gilles,
    Re: "Really? why has it cooled meanwhile, then ? "

    Uh, CO2 levels went down?

    What makes you think that the planet will behave differently now than it has under similar conditions in the past?


    You are asking us to spoon feed you information that you can readily look up yourself.

    Examples:
    Damaging effects
    ocean+acidification
    Hadley+Cell
    heat+crop+production
    (The one on plant stress is very pertinent.)

    Or, maybe you should examine the links between the Russian heat wave last year and unrest in the Middle East this year. Hint: Where did Russia used to sell a lot of wheat in prior years?

    What causes CO2 levels to change and how does that affect the climate?

    You are diverging from a reasonable argument with holes in it into something else. You have asked repeatedly what, other than man, causes changes in CO2 levels, and repeatedly you been directed how to find that information. Please quit asking the same question.

    Yes, quantitative, that is what this article and others like it are about.

    Sometimes I find this useful:
    Rational Discussion Rules
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  37. 33, Gilles,
    Really? why has it cooled meanwhile, then ?

    If you need to ask this, then you have some studying to do.
    As far as I know, the huge increase of population is correlated with an increase of FF consumption and an increase of temperature...

    One upon a time, my own height was well correlated with my age. As I aged, I grew. I should probably be about 100ft tall by now.
    ...please give me a simple argument to tell me when the negative effect of an increase of temperature would be much larger...

    Because extreme increases in temperature will result in major desertification and other ecosystem changes, as well as the alteration of climate zones (i.e. growing seasons).

    More importantly, major changes in precipitation patterns and large, difficult to endure droughts will greatly reduce crop productivity, leading to widespread famine.

    It certainly won't help, either, when the productivity of the ocean as a food source plummets because of acidification.

    This will probably take 50 to 100 years, but once it starts, there will be no going back.

    This is the game that you are so callously playing with civilization.

    Now can you please go back to the topic, instead of dragging the thread into your own personal conversation about whatever you want to talk about?
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  38. @33 Gilles:

    "would survive what ?"

    Gilles, you do amaze me.

    To your first question as to what humanity would survive (give me some time to chuckle) he simple answer was given when I described Lovelock as a believer (Me too) of CAGW. Spelled out that means "Catastrophic Anthropogenic Global Warming"

    No, I'm not one for meticulous and mathematical details but I'll throw this in. 10 degrees Fahrenheit above pre-industrial levels.

    I seriously don't think that this civilization will not go over 600 ppm because economic downturn/collapse (sometime before we reach 600 ppm) brings our consumption spiralling down.

    That may not be enough for a 10F increase but then there are pesky things like the Siberian permafrost/defrost. Please see video below.

    "http://www.youtube.com/watch?v=vSLHvZnbYwc&feature=related


    "As far as I know, the huge increase of population is correlated with an increase of FF consumption and an increase of temperature - so if any, the "negative" influence of increasing temperature has been largely offset by the positive effect of energy availability - or the huge modern demographic growth would be totally incomprehensible."

    Gilles, it's the use of FF that is digging our graves.

    Incomprehensibility of population growth is irrelevant. I know it is due to Carl Bosch developing the conversion of natural gas to synthetic fertilizers in 1913. So what? To use an analogy, you can grow fat on junk food; then you die.

    As for negative effects being counterbalanced by "positive" effects, tell that to the Egyptians who pay 40% of their salaries for staple foods. Let's connect the dots. There have been multiple crop failures throughout the world causing a spiraling in grain prices.

    Winter/Summer of 2010/2011:

    a. Russia/Ukraine: Up to 40% failure of wheat crop due to severe drought and high temperatures. They are major wheat exporters.

    b. Pakistan: 20% of its land inundated by floods. They had to import food.

    c. Australia: Major damage to wheat crops due to intense rains (from warming oceans). They are a major wheat exporting nation.

    d. Argentina: Soybean and corn crop loss due to drought.

    e. Canada: Damage to wheat crop due to intense rains. They too, are a major wheat exporting nation.

    f. China: Loss of almost the entire winter wheat crop. Neither an exporter or importer of wheat, China has been self sufficient in that crop. Not that it matters because they have a huge population that will need to import grains.

    g. Mexico: Major loss of corn crop. They have had to import 50% more corn from the US than previously.

    No; it's not the individual crop failures that can be pinned to AGW; it's the number and frequency. Expect more of he same throughout the rest of this decade.

    It's up to you to calculate the "negative" effects (quote marks yours).

    Now please give me a simple argument to tell me when the negative effect of an increase of temperature would be much larger that the positive effect of increasing energy consumption -and conversely the positive effect of avoiding the increase of temperature would be much larger that the negative effect of suppressing 80 % of the energy consumption- since the whole history demonstrates exactly the opposite ?" [Underlining mine]

    "It's this simple, Gilles. It's already happening. Furthermore, your concept of the "positive" effects of FF, irrespective of the AGW issue, is questionable; but that's another story.

    As far as the negative effect of decreasing our consumption of FF by 80%, I am of the opinion that we have to cut our consumption by 90% within the next 10 years.

    That is enough to make some of the forum members here gulp. Of course, 'Skeptics' will get a hernia (due to intense laughter) when they hear that.

    But this is how I perceive the situation. If we take the "extreme" measure of reducing FF consumption by 90% in the next decade, then we will get our teeth kicked in by AGW. No ifs, ands or buts.

    This will be, in major part, due to the Arctic Ice Cap shrinkage and its drastic effects on our climate in the Northern Hemisphere. This will include the acceleration of the Siberian permadefrost, and the subsequent increase in the metabolism of the methanogens that are releasing ... methane. Positive feedback, you know.

    It's too late to stop that IMO. The Arctic Ice Cap went past the tipping point long ago. Those who say otherwise are probably not taking the 1F of increased heat that we're due in the next 30 years. That assumes that we magically stop all FF emissions cold and right this minute. Thermal lag you know.

    However, if we don't take the drastic actions I've proposed or we take symbolic and token actions (as I predict will happen by decade's end) then we're going to get our teeth kicked in and, a few decades down the road, our skulls bashed in.

    Nice choice, isn't it?

    Bottom line, Gilles, you don't calculate and scratch your head when it's time to slam the brakes.

    I hope this answer has been simple enough. I'm sure I forgot a few things, however.


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  39. 34 : climate has never cooled after Pliocene ?

    35 : I don't think your answer is really one, since world population has increased by several billions - it may BTW be interesting to know that the 30000 deaths have been almost compensated by a corresponding decrease the year after, most of them being old people having shortened their life by a few months. Sad enough, but you don't intend to be immortal do you ? and do you really hope avoiding all this kind of events by reducing FF ?

    "Uh, CO2 levels went down?" : yes but .. why ?

    37 : my point was the rise of temperature didn't prevent population from growing - i did not state that it grew thanks to FF , ( although it is pretty obvious), but that temperature did not prevent it.

    So my question was : when will it do it ?

    Now it this OT, you should have said that to Villabolo already at #9 and #31 - why do you notice only my answers ?

    Concerning Pliocene, I'm far from being an experts, but some googling led me for instance to that :

    "In addition to the above experiment, several simulations were conducted using increased levels of atmospheric carbon dioxide; higher CO2 amounts have also been proposed as a potential cause of the warmer Pliocene climates (Crowley, 1991). Rind and Chandler, (1991) pointed out that SST patterns such as the one seen in the Pliocene are inconsistent with CO2 generated warming, however, it is possible that some combination of CO2 increase and ocean heat transport change could have resulted in the warmer Pliocene surface temperatures. Figure 3 shows the various levels of ocean heat transport required to generate the PRISM SSTs given various atmospheric CO2 increases. The graph indicates that with modern ocean heat transports (0% increase) CO2 levels must have been at least 1400 ppm (4.5 times the modern value) in order to generate the global warming of the Pliocene. So far, estimates based on carbon isotope measurements by Raymo and Rau (1992) suggest that Pliocene CO2 levels were, at most, 100 ppm greater than today."

    well, I don't know if they're right, but it seems that they claim that CO2 is responsible only of 10 % of the warming or so (much in line with what I explained on feedbacks :) at least it is a possibility , which means that it is by no way granted that it makes sense to compare CO2 levels and temperatures to current ones. Comments ?
    0 0
    Moderator Response: [Muoncounter] An astonishing reply, Gilles, even for one with your track record. Heat wave deaths among the elderly are 'compensated' for the following year? Nice compassionate worldview you have.
  40. @ Gilles:

    "as is rather usual in climate discussion, it seems that you would like to live in a world without any problem? without heat wave, crop failures, without poverty, without deaths, without bad trolls on your favorite web site ...

    I can understand it, but isn't it a little bit ... childish ?"


    Gilles; I really don't care about the 'trollism'. What I do mind is your seeming lack of understanding of basic AGW points. It is not an issue of whether you agree with those points but rather that you either don't acknowledge them and carry the conversation from there, or that you are actually ignorant of them.

    That puts us in the exasperating position of having "to spoon feed" you, as Chris G said.

    As far as living in a world without any problems, the issue is not the usual problems that have been happening in the past but the obvious prospect of severely escalating problems in the future.

    We're talking about billions of people. Last time we lost 1/4 of our population, throughout Eurasia, it was due to a few rats, and their fleas, per person. Think of how easy it would have been to prevent that.

    Isn't it childish to engage in magical thinking and wish a thunderstorm away?





    "One can always do a list of everything that went wrong these last years : what does it prove ? what's the use of all these cherry-picked events ? and what went worse was not that - it was mainly..earthquakes, you know."

    As far as cherry picking is concerned, Gilles, that is when you take facts out of the context of the big picture in order to give a distorted view of things.

    On the other hand, highlighting is what you do when you have presented the big picture first and then focus on a fact in context of that picture.

    One can rarely give the big picture on this subject, in conversations like this. That is due to the enormity of the issues. Yet, you are supposed to know what those issues are in detail if you come to this forum to discuss them.

    As far as your statement that earthquakes killed more people in the past few years that is both irrelevant and it also qualifies as cherry picking. You are concentrating on a natural event that is sporadic in a given time period versus human distorted 'natural' events which are increasing on a year by year level.

    Besides, you have not responded to the issue of Arctic Ice cap shrink and its effects in the near future. However that is definitely off topic and should be dealt with elsewhere.

    So I will briefly steer this wayward thread back into its original course.

    Compare the Pliocene's arid ecology in North America and please tell me; do you want a bumper crop of corn in Kansas or would you prefer a bumper crop of cactus?

    Expect that to happen with our business as usual policy within the lifetimes of our grandchildren.
    0 0
  41. Gilles wrote : "34 : climate has never cooled after Pliocene ?"


    Oh, is that what you meant ? You are not very clear sometimes and I would suggest that is most of your problem, unfortunately. Your English is good but not as good as you think.
    0 0
  42. Wow Gilles, you're an even bigger piece of work than I thought you were-& that's really saying something. Here you've been, telling us over scores of postings, how you believe consumption of fossil fuels is necessary to save the lives of people in the developing world-yet clearly you don't give two hoots about human life, you only care that the world consumes more of your precious fossil fuels, & damn the consequences.

    Also, like any good denialist, you believe that repeating the same myths will somehow make them true-like your false FF consumption correlates with population growth meme. Well guess what? It was wrong before, & its still wrong now. China has had a much bigger growth rate than the Western Hemisphere-dating back to the middle ages. Was that because they had coal-fired power stations the European World wasn't aware of? No, its because they had much better medicine, education & sanitation than the Europeans. Its also funny that China's growth rate, over the last 30 years, has been less than any time during at least the last 500 years-yet their fossil fuel consumption in the last 30 years has been at its highest during that same time-frame. Kind of knocks your ill-founded "correlation" fantasy on the head, doesn't it?
    Similarly, population growth rates in the West actually started to climb significantly around the end of the 18th/start of the 19th century. Again, improvements in health care, sanitation & income distribution seem to be the most likely causes. Also, according to what I've seen, yearly growth rates have fallen from around 2% per year in 1970 down to around 1.2% per year in 2010-not exactly great evidence for your "correlation" myth, is it Gilles?
    Last of all, in recent history some of the biggest population growths have occurred in Countries like Thailand, The Philippines, Brazil & Mexico-in spite of the fact that their fossil fuel consumption remain far lower than those of the less populous, so-called "advanced" economies of Western Europe & North America. Again, not great "evidence" for your "correlation" myth.

    It seems you understand historical correlations about as well as you understand the drivers of climate change & release & take-up of greenhouse gases. That is to say-you don't understand them *at all*, & should probably go & educate yourself before you embarrass yourself even further.
    0 0
    Moderator Response: [DB] Your spirit is appreciated, but your energy is better served someplace where productive results are achievable. Unfortunately, this is not one of those. DNFTT.
  43. I'm sorry for english, "meanwhile" wasn't the appropriate word :) so why did the world cool after Pliocene ?

    Now i'm rather stupefied by the number of false and unsubstantiated statements I can read in your answers - it's unfortunately a little bit lengthy to answer all, so please forgive me if I forget some.
    "the obvious prospect of severely escalating problems in the future." : well obvious if you believe in them, and if you're formatted by the impressive number of dire predictions that are made everywhere - but actually there is no "obvious" fact about an imminent catastrophe. recent example drawn from a competitor site

    http://asiancorrespondent.com/52189/what-happened-to-the-climate-refugees/

    maybe we'll soon have here a post on this subject ?

    "You are concentrating on a natural event that is sporadic in a given time period versus human distorted 'natural' events which are increasing on a year by year level."

    ... which human distorted natural events are increasing on a year to year level ? well , they're probably "human distorted" but not quite in the same sense ...

    "Besides, you have not responded to the issue of Arctic Ice cap shrink and its effects in the near future. "

    I have some difficulties to imagine why the Arctic ice cap shrinking has caused any harm in the millions of people living around me ... didn't we talk about the disappearance of 99 % of the human population ? do you mean that 99% will commit suicide because of polar bears or what ?

    "Compare the Pliocene's arid ecology in North America and please tell me; do you want a bumper crop of corn in Kansas or would you prefer a bumper crop of cactus?"
    My issue that it was not relevant to equate = level of CO2 = climate, several millions years ago, so why should I answer an irrelevant question ?

    Marcus " you only care that the world consumes more of your precious fossil fuels,"

    As my point is precisely that it won't , I have some difficulties to understand why you say that.

    " China has had a much bigger growth rate than the Western Hemisphere-dating back to the middle ages."

    Really ? what was the average growth rate of China between, say , 1000 and 1800, following you ? Hint : the average growth rate of A(t) in the [t0,t1] interval is ln[A(t1)/A(t0)]/(t1-t0).

    "ts also funny that China's growth rate, over the last 30 years, has been less than any time during at least the last 500 years-"

    do you realize what an exponential growth really means ? the current rate is around 1%, giving a doubling time of 70 years. 500 years of 1% growth rate makes 2^(500/70) = 141 , so now we learn that China had less than 10 millions inhabitants in 1500 ?
    actually here is the real growth of population
    (http://afe.easia.columbia.edu/special/china_1950_population.htm)

    very far from your figures ) and nearly flat during the Middle Age. The growth started just before the industrial revolution, indeed, but it is remarkable that it exhibits some "hockey stick" shape correlated .. positively with temperature !

    But I did never stated that population could only grow thanks to FF, although I think they're quite a part of it (it is not necessary to have much FF - it's enough to avoid famines through agricultural productivity): what I stated that I saw no sign, nowhere, that a growing temperature produced a decrease in the population. Can you stick on this assertion ?
    0 0
  44. "But I did never stated that population could only grow thanks to FF"

    Yes you have, on more than one occasion-you only ever claim that's not the case when people finally blow your claims clear out of the water. The graph you provide doesn't exactly help your case-given that the population growth really got going during the 16th century & onwards. Also, I never said China's growth rate was huge in the middle ages-just signficantly larger than that of Europe during the same period. China's population growth rate post 1970's *is* lower than what it was previously-I can't help the fact that you refuse to accept that fact. My other points, which you can't even be bothered to address, merely highlight how weak your entire case is.

    "what I stated that I saw no sign, nowhere, that a growing temperature produced a decrease in the population"

    As someone who works in the Agricultural Science sector, I can assure you that ongoing temperature rises *will* continue to have an ongoing negative impact on crop outputs. Technological fixes can alleviate this to some degree, but only at a much increased price for staple goods. Now if you think a world of increased crop failures & more expensive foodstuffs is good for a world which is already failing to feed its entire population, then you're simply much, much more deluded than I ever thought.
    0 0
  45. 44 : Marcus : please substantiate your personal attacks, at least. I never stated that population could grow only through FF, and if you say the opposite, show me where. Now YOU said "China has had a much bigger growth rate than the Western Hemisphere-dating back to the middle ages."
    And I asked you : "what was the average growth rate of China between, say , 1000 and 1800, following you ?"
    can you at least answer that ?

    "As someone who works in the Agricultural Science sector, I can assure you that ongoing temperature rises *will* continue to have an ongoing negative impact on crop outputs."

    And as someone who works in the Agricultural Science sector, are you stating that the price and the availability of FF has no influence on the crop outputs and the price of food ?

    The problem we're facing now is just demographic expansion - actually we've escaped Malthus' dire prediction for some centuries thanks to the discovery of new territories and the use of FF (yes), but we meet the problem again - and it was unescapable because exponential growth meets always a limit. That's all, and that's enough - warming has nothing to do with that, it can make the problem worse at some places, but it is very far from being the main problem. The main problem is simply overpopulation, and even if we suppressed totally FF, we'd have to face it anyway. Do not mix up the issues.
    0 0
    Moderator Response: [muoncounter] This is not a thread about historic population growth. Further off-topic diversions will be deleted.
  46. @42 Moderator:

    "Moderator Response: [DB] Your spirit is appreciated, but your energy is better served someplace where productive results are achievable. Unfortunately, this is not one of those. DNFTT"

    Please Moderator; I promise to stop the feeding frenzy. From now on I beg you to bind and gag me whenever he posts!

    ****************************************************
    @43 Gilles:

    One last time through this Gish Gilles Gallop and then I'll stop beating these dead horses:

    Now i'm rather stupefied by the number of false and unsubstantiated statements I can read in your answers - it's unfortunately a little bit lengthy to answer all, so please forgive me if I forget some.
    "the obvious prospect of severely escalating problems in the future." : well obvious if you believe in them, and if you're formatted by the impressive number of dire predictions that are made everywhere - but actually there is no "obvious" fact about an imminent catastrophe. recent example drawn from a competitor site

    http://asiancorrespondent.com/52189/what-happened-to-the-climate-refugees/

    maybe we'll soon have here a post on this subject ?


    "Obvious" is based on deductive reasoning based on a wide assortment of facts that you seem to be ignorant on.

    "You are concentrating on a natural event that is sporadic in a given time period versus human distorted 'natural' events which are increasing on a year by year level."

    ... which human distorted natural events are increasing on a year to year level ? well , they're probably "human distorted" but not quite in the same sense ...


    (As I let out a loud sigh). The escalation in temperatures during the last several decades; increase in rain intensity...Deja vu, am I repeating myself? Never mind Gilles.

    "Besides, you have not responded to the issue of Arctic Ice cap shrink and its effects in the near future. "

    I have some difficulties to imagine why the Arctic ice cap shrinking has caused any harm in the millions of people living around me ... didn't we talk about the disappearance of 99 % of the human population ? do you mean that 99% will commit suicide because of polar bears or what ?


    Why not throw another biscuit in your direction?

    1. Light reflecting Arctic ice cap is shrinking and thinning, exposing heat absorbing water.
    2. More heat generated by albedo flip = greater water evaporation intensifying amount of rain and strength of storms which are fueled by the extra heat.
    3. Crop and infrastructure damage throughout the Northern Hemisphere due to intense rains and changes in weather patterns.
    4. This Arctic Sea exposure thus adding to the already present intensiication in rain and snow due to the temperature increase of other oceans.
    5. Temperature increase in an ice free summer Arctic Sea leading to (More deja vu) increase in regional warmth.
    6. Which includes Siberia, whose permafrost is melting and releasing Methane (You do know that Methane is a Greehouse gas-don't you?).
    7. The increase in Siberia's heat thus amplifies the permafrost melt and methanogen microbial metabolism leading to an escalation in the rate of increase in the release of Methane. I think that's called a positive feedback loop.

    You may now brush off all of the above.


    "Compare the Pliocene's arid ecology in North America and please tell me; do you want a bumper crop of corn in Kansas or would you prefer a bumper crop of cactus?"
    My issue that it was not relevant to equate = level of CO2 = climate, several millions years ago, so why should I answer an irrelevant question ?


    Yawn! Feeding time over.
    0 0
    Moderator Response: [Dikran Marsupial] Please can we moderate the tone back to "impersonal scientific discussion" (I know there is an element of "pot meet kettle" there, for which I apologise).
  47. OK but am I allowed to answer villabolo's points or not ?
    0 0
    Moderator Response: [Dikran Marsupial] As long as you stick to comparison of climate yes; if it relates to whether the change will be bad for mankind, respond to them on "its not bad", where they would be more appropriate. Please also pay attention to the comment I left on Villalobo's post.
  48. [inflamatory comments deleted]

    I'm far more interested to know whether or not we have a good idea how much ice there was before the temperatures started rising during the Pliocene?

    Also, a recent study claims that the current CO2 levels are the highest in 15 million years, see here.

    If that is true, as are the findings discussed by Bart Verheggen here, then I really do not see much reason for the optimism and glib attitude shown by our dear contrarians.
    0 0
    Moderator Response: [Dikran Marsupial] Please see the comment on Villalobos' post; the discussion is best served if we all keep the tone neutral, whatever the perceived provocation.
  49. Dikran; not a problem. However my name is Villabolo not Villalobo.

    "Lobo" means wolf in Spanish.
    0 0
  50. I know its OT, but am I the only one whose noticed that-the moment Gilles was required to remain On topic-he has had nothing further to add to the conversation?
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